Determination of a match between data values stored by three or more arrays

ABSTRACT

Apparatuses, systems, and methods related to determination of a match between data values stored by three or more arrays are described. A system using the data values may manage performance of functions, including automated functions critical for prevention of damage to a product, personnel safety, and/or reliable operation, based on whether the data values match. For instance, one apparatus described herein includes a plurality of arrays of memory cells formed on a single memory chip. The apparatus further includes comparator circuitry configured to compare data values stored by three arrays selected from the plurality to determine whether there is a match between the data values stored by the three arrays. The apparatus further includes an output component configured to output data values of one of two arrays of the three arrays responsive to determination of the match between the data values stored by the two arrays.

TECHNICAL FIELD

The present disclosure relates generally to semiconductor memory and methods, and more particularly, to apparatuses, systems, and methods for determination of a match between data values stored by multiple arrays.

BACKGROUND

Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic systems. There are many different types of memory, including volatile and non-volatile memory. Volatile memory can require power to maintain its data (e.g., host data, error data, etc.). Volatile memory can include random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), synchronous dynamic random access memory (SDRAM), and thyristor random access memory (TRAM), among other types. Non-volatile memory can provide persistent data by retaining stored data when not powered. Non-volatile memory can include NAND flash memory, NOR flash memory, and resistance variable memory, such as phase change random access memory (PCRAM) and resistive random access memory (RRAM), and magnetoresistive random access memory (MRAM), such as spin torque transfer random access memory (STT RAM), among other types.

Electronic systems often include a number of processing resources (e.g., one or more processors), which may retrieve instructions from a suitable location and execute the instructions and/or store results of the executed instructions to a suitable location (e.g., the volatile and/or non-volatile memory). A processor can include a number of functional units such as arithmetic logic unit (ALU) circuitry, floating point unit (FPU) circuitry, and a combinatorial logic block, for example, which can be used to execute instructions by performing logical operations such as AND, OR, NOT, NAND, NOR, and XOR, and invert (e.g., NOT) logical operations on data (e.g., one or more operands). For example, functional unit circuitry may be used to perform arithmetic operations such as addition, subtraction, multiplication, and division on operands via a number of operations.

In many instances, the processing resources may be external to the memory device (e.g., including a number of memory arrays) and the data may be accessed via a bus between the processing resources and a memory array to execute a set of instructions. However, one or more errors in storage and/or accessing of data values in the instructions and movement of such data values from the bank to a processor external to the memory device may influence whether the instructions may be executed as intended for performance of an operation by an external processing resource.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic diagrams illustrating examples of redundantly storing a single data file on at least three arrays in accordance with a number of embodiments of the present disclosure.

FIG. 2 is a block diagram of examples of arrays of memory cells on a portion of a memory device in accordance with a number of embodiments of the present disclosure.

FIG. 3 is a schematic diagram illustrating an example of circuitry for comparing data values stored by three arrays in accordance with a number of embodiments of the present disclosure.

FIG. 4 is a schematic diagram illustrating an example of a comparator component in accordance with a number of embodiments of the present disclosure.

FIG. 5 is a schematic diagram illustrating an example of three arrays selectably coupled to comparator circuitry in accordance with a number of embodiments of the present disclosure.

FIG. 6 is an example of logic for determination of whether there is a match between data values stored by three arrays in accordance with a number of embodiments of the present disclosure.

FIG. 7 is an example of logic for selection of one array for output of matched data values in accordance with a number of embodiments of the present disclosure.

FIG. 8 is a flow chart for determination of a match between data values stored by three arrays in accordance with a number of embodiments of the present disclosure.

DETAILED DESCRIPTION

The present disclosure includes systems, apparatuses and methods associated with determination of a match between data values stored by multiple arrays. In a number of embodiments, an apparatus includes a plurality of arrays of memory cells formed on a single memory chip. The apparatus further includes comparator circuitry configured to compare data values stored by three arrays selected from the plurality to determine whether there is a match between the data values stored by the three arrays. The apparatus further includes an output component of the comparator circuitry configured to output data values of one of two arrays of the three arrays responsive to determination of the match between the data values stored by the two arrays.

Being formed on a single memory chip (e.g., on chip) is intended herein to mean being formed (e.g., positioned) on a same chip as a memory array (e.g., an “array” as shown at 108 and described in connection with FIGS. 1A and 1B and elsewhere herein). Array as used herein is a general term intended to include bank groups 213, banks 214, and/or bank sections 216 shown in and described in connection with FIG. 2 (e.g., in a DRAM configuration, although memory arrays are not limited to being in the DRAM configuration). In a number of embodiments, the bank sections 216 may correspond to “subarrays” of a DRAM memory array and/or bank.

In contrast, being formed on a different chip (e.g., off chip) is intended herein to mean being formed (e.g., positioned) on a chip associated with execution of instructions (e.g., coded in a sequence of data values) received (e.g., sent) from on chip for performance of an operation by an external processing resource (e.g., a functionality as shown at 338 and described in connection with FIG. 3 and elsewhere herein). A monitor component (e.g., as shown at 339 and described in connection with FIG. 3 and elsewhere herein) also may be formed off chip (e.g., coupled to, or part of, at least one functionality 338) to receive a notification of a determination of no match between the data values for the instructions stored by the three arrays.

Performance of functions based upon execution of sequences of data values (instructions) stored by and accessed from memory arrays may be an integral part of many automated systems. A system using the data values may manage performance of functions, including automated functions critical for prevention of damage to a product, personnel safety, and/or reliable operation, based on whether the data values match. Proper performance of the functions contributing to the automated systems may be critical for prevention of damage to a product including such automated systems (e.g., autonomous vehicles, such as automobiles, trains, airplanes, rockets, space stations, etc., among many other possibilities) and/or safety of a person (e.g., a passenger of an autonomous vehicle, a bicyclist, a pedestrian, an observer, etc., among many other possibilities) using and/or near such automated systems.

Hence, automated systems utilized in such implementations may benefit from lower error rates in stored data values to be executed for performance of the functions contributing to the automated systems (e.g., relative to error rates considered acceptable for other utilities, such as cellular telephones, smart phones, personal computers, etc.). Accordingly, the determination of a match between the data values (instructions) redundantly stored by the three arrays and/or the notification of no such match described herein may enhance prevention of damage to products including such automated systems and/or safety of persons using and/or near such automated systems.

The figures herein follow a numbering convention in which the first digit or digits of a reference number correspond to the figure number and the remaining digits identify an element or component in the figure. Similar elements or components between different figures may be identified by the use of similar digits. For example, 108 may reference element “08” in FIG. 1A, and a similar element may be referenced as 308 in FIG. 3.

FIGS. 1A and 1B are schematic diagrams 100 illustrating examples of redundantly storing a single data file on at least three arrays in accordance with a number of embodiments of the present disclosure. Three arrays of memory cells are represented by array X at 108-0, array Y at 108-1, and array Z at 108-2, although in a number of embodiment a single data set or file 102 may be stored in more than three arrays and three arrays may be selected therefrom for comparison of the data values, as described herein. The single data file 102 may be, or may include, a number of data values encoded as instructions to be executed for performance of an operation (e.g., braking, accelerating, turning, etc., for controlling progress of an autonomous vehicle toward arrival at an intended destination, among many other possibilities). The single data file 102 referred to herein may also, or alternatively, be referred to as data, a data set, or the like. Data also may include control information or executable instructions, in various contexts.

The single data file 102 may be received from, for example, a host (not shown), using a k-bit data bus 104, where k may represent a number of data values (bits) in the single data file 102 to be received at a time (e.g., in one cycle of a computer). In a number of embodiments, the number of data values received by the k-bit data bus 104 may be 16, as in the example shown in FIGS. 1A and 1B, although embodiments are not limited to a 16 bit data bus.

The k bits of data may be deserialized into a number (n) of portions using a deserializer 105 coupled to the k-bit data bus. The n portions of the k bits of data may be moved (e.g., electronically transported) via a kn-bit data bus 107 to at least one of the three arrays (e.g., to array 108-0, array 108-1, and/or array 108-2). In a number of embodiments, the number of data values moved via the kn-bit data bus 107 may be 256 (=16×16), as in the example shown in FIGS. 1A and 1B, although embodiments are not limited to a 256 bit data bus. The n portions of the k bits of data may be redundantly stored on the three arrays as the single data file 102.

As shown in FIG. 1A, in some embodiments, the single data file 102 may be redundantly stored in parallel on the three arrays via three sets of data lines (e.g., kn-bit data buses 107-0, 107-1, and 107-2) separately coupled to the three separate arrays (e.g., array 108-0, array 108-1, and array 108-2, respectively). The kn-bit data buses 107-0, 107-1, and 107-2 each may be a number of physical data lines that move the redundant single data file (e.g., duplicate data values) to each of the three separate arrays 108-0, 108-1, and 108-2.

As shown in FIG. 1B, in some embodiments, the single data file 102 may be stored on a first array (e.g., array 108-0) of the three arrays via a set of data lines 107 coupled to the first array. A copy function 109 may be performed on the single data file stored on the first array 108-0 to redundantly store the single data file 102 on a second array 108-1 and on a third array 108-2 of the three arrays.

FIG. 2 is a block diagram of examples of arrays of memory cells on a portion of a memory device 210 in accordance with a number of embodiments of the present disclosure. As described herein, a plurality of arrays of memory cells may be formed on a single memory chip. The portion of the memory device 210 shown in FIG. 2 may be formed (e.g., included) on the single memory chip (e.g., may be on chip). Being on chip also is intended, in a number of embodiments, to mean being formed on the same chip as a controller 211 and/or sensing circuitry 212 coupled to the plurality of arrays.

The controller 211 (e.g., bank control logic and sequencer) may include control circuitry, in the form of hardware, firmware, or software, or combinations thereof. As an example, the controller 211 may include a state machine, a sequencer, and/or some other types of control circuitry, which may be implemented in the form of an application specific integrated circuit (ASIC) coupled to a printed circuit board. In a number of embodiments, the controller 211 may be co-located with the host (not shown) (e.g., in a system-on-chip (SOC) configuration).

The host and/or a dedicated component may include a number of processing resources (e.g., one or more processors, microprocessors, or some other type of controlling circuitry) external to the chip (off chip) on which the memory device 210 is formed. The external processing resources may be capable of accessing the memory device 210 (e.g., via controller 211) to perform operations on data values moved from the memory device 210. At least some of the operations may be performed by various functionalities (e.g., the functionality as shown at 338 and described in connection with FIG. 3 and elsewhere herein) associated with the host and/or the dedicated component. Controller 211 also may, in a number of embodiments, include a number of processing resources for performance of processing operations. The controller 211 may perform address resolution for an entire block of instructions (e.g., commands associated with executing instructions encoded in a single data file) and data and direct (e.g., control) allocation and storage of data and commands into allocated locations in the arrays (e.g., bank groups 213, banks 214, and/or bank sections 216) and/or to an external destination.

The sensing circuitry 212 may be configured to sense data values stored by the arrays (e.g., by being selectably coupled to a particular row of memory cells in an array). The sensed data values may be made accessible to comparator circuitry (e.g., as shown at 332 and described in connection with FIG. 3 and elsewhere herein) configured to compare data values of the single data file 102 stored by the at least three arrays to determine whether there is a match between the data values stored by a plurality of arrays of the at least three arrays. The match may be between data values stored by two arrays of three arrays in which the data values are redundantly stored, although comparisons may be made for a match between three of four arrays, three of five arrays, and/or four or five of six arrays, etc. Given the possibility of an error in the data values of the single data file 102 stored by at least one array, and that no match may be determined if the data values are stored by the array with the data error and only one other array, the probability of determining a match between arrays is increased when the data values are stored by at least three arrays.

The controller 211 may be configured to receive a request (e.g., from the host and/or the functionality 338) for the stored single data file 102. The controller 211 may, in a number of embodiments, be configured to direct the comparator circuitry 332 to access the data values stored by the at least three arrays to determine whether there is a match in a plurality of arrays.

Being on chip also may, in a number of embodiments, be intended to mean being formed on the same chip as the comparator circuitry 332, which may include the output component (e.g., as shown at 333 and described in connection with FIG. 3 and elsewhere herein). Being on chip also may, in a number of embodiments, be intended to mean being formed on the same chip as the deserializer 105 and/or a serializer (e.g., as shown at 334 and described in connection with FIG. 3 and elsewhere herein), along with associated data lines (e.g., buses 104 and 107).

The plurality of arrays 108 formed on chip with the memory device 210 and on which the single data file 102 is redundantly stored by at least three arrays may be variously implemented. In a number of embodiments, the at least three arrays may each correspond to a different bank group formed on chip (e.g., bank groups 213-0, 213-1, 213-2 and 213-N, although the number of different bank groups is not limited to four). Each different bank group may have a plurality of memory banks formed on chip (e.g., banks 214-0, 214-1, 214-2 and 214-M, although the number of banks is not limited to four). In a number of embodiments, the at least three arrays may each correspond to a different bank formed on chip. The different banks may be selected from banks 214-0, 214-1, 214-2 and 214-M. In a number of embodiments, the at least three arrays may each correspond to a different section (e.g., sections 216-0, 216-1, 216-2 and 216-P, although the number of sections is not limited to four) of a single bank (e.g., bank 214-0, among other possible banks) formed on chip.

In various embodiments, any three or more of the plurality of bank groups 213-0, . . . , 213-N, of the plurality of banks 214-0, . . . , 214-M, and/or the plurality of sections 216-0, . . . , 216-P at various positions on chip may be selected for redundant storage of the single data file 102 and/or for comparison of the data values stored thereon for determination of a possible match. Determination of the arrays on which to store the single data file 102 may be influenced by the size (e.g., number of data values) of the single data file, among other possible considerations. By way of example, three out of four of the bank groups 213 shown in FIG. 2 may be selected, three out of four banks 214 in bank group 213-0 may be selected or one bank in each of three different bank groups may be selected, and/or three out of four sections 216 in bank 214-0 may be selected or one section in each of three different banks may be selected, among other possible selections of the three arrays.

In a number of embodiments, the at least three arrays selected from the plurality for redundant storage of the single data file 102 may each be formed on chip in a DRAM configuration. Implementations of the circuitry described herein may be utilized for determination of a match between data values stored, for example, by two out of three arrays in the DRAM configuration conforming to protocols such as those promulgated by JEDEC, including DDR3, DDR4, etc.

Depending upon the architecture of the memory device 210 and/or the arrays 213, 214, 216 on chip, the arrays upon which the single data file 102 is redundantly stored may not be physically close (e.g., adjacent and/or contiguous) to each other. For example, accounting for routing and/or die size considerations, the arrays 213, 214, 216 may be physically separated from each other (e.g., via channels 217 and/or 219)

FIG. 3 is a schematic diagram illustrating an example of circuitry 330 for comparing data values stored by three arrays in accordance with a number of embodiments of the present disclosure. As described herein, a plurality of arrays of memory cells may be formed on chip 336 and a single data file 102 may, in some embodiments, be redundantly stored by each of three arrays (e.g., array X at 308-0, array Y at 308-1, and array Z at 308-2) of the plurality of arrays. The plurality of arrays, including the three arrays 308-0, 308-1, and 308-2, may, in a number of embodiments, each be formed in a same configuration of memory cells on chip 336. The same configuration may facilitate comparison and matching by the comparator circuitry 332 of the redundantly stored data values accessed from the three arrays 308-0, 308-1, and 308-2 via respective data lines (e.g., kn-bit data buses) 307-0, 307-1, and 307-2.

For example, each of the plurality of arrays (e.g., as shown at 213, 214, and/or 216 and described in connection with FIG. 2) may be configured as DRAM circuitry in which each of the bank groups 213 may include the same number of banks 214 and each of the banks 214 may include the same number of sections 216 (e.g., subarrays). Each bank 214 and/or section 216 may include the same number of rows of memory cells. Each row may include the same number of memory cells, by which each bank 214 and/or section 216 may include the same number of columns of memory cells. The memory cells in the DRAM configuration may each be formed as a one access device (e.g., transistor) and one storage element (e.g., capacitor) 1T1C memory cell that each may be coupled to a sense amplifier (not shown) in the sensing circuitry 212. However, embodiments are not so limited, such that some embodiments may have memory cells in a 2T2C DRAM configuration (e.g., in which each memory cell may be coupled to the sense amplifier and/or a compute component (not shown) in the sensing circuitry 212) or in other configurations (e.g., a 3T configuration, among other possible configurations).

Comparator circuitry 332 may be configured to compare data values stored by the three arrays 308-0, 308-1, and 308-2 selected from the plurality of arrays to determine whether there is a match between the data values stored by at least two arrays of the three arrays. As described herein, a single data file 102 may be redundantly stored by each of the three arrays and the comparator circuitry 332 may be configured to compare data values of the single data file stored by the three arrays. The comparator circuitry 332 may be formed (e.g., positioned) on chip 336 with the plurality of arrays. The comparator circuitry 332 may be positioned in various locations on chip 336 (e.g., accounting for routing and/or timing considerations).

The comparator circuitry 332 may be further configured to determine whether there is the match between the data values based upon an adjustable threshold number of mismatches and/or positions of such mismatches of data values in the single data file 102 stored by two of the arrays. In a number of embodiments, the adjustable threshold number of mismatches may be 0-10 mismatches, which may be adjusted based upon a number of parameters (e.g., the number of data values in the single data file 102). The adjustable threshold number may be adjusted to no mismatches (0 mismatches). For example, 0 mismatches may be selected as the threshold number when proper performance of an operation enabled and/or controlled by a functionality 338 may affect safety of passengers and/or bystanders (e.g., braking and/or evasive maneuvers of an autonomous automobile to avoid collision with another automobile and/or pedestrian, among many other possible operations). Accordingly, the plurality of arrays of memory cells and/or the comparator circuitry 332 formed on chip 336 may be formed (e.g., located) on an autonomous vehicle, among various other possible locations and/or implementations.

An output component 333 of the comparator circuitry 332 may be configured to output data values of one of two arrays (e.g., from either array 308-0, array 308-1, or array 308-2) of the three arrays responsive to determination of the match between the data values stored by the two arrays. For example, as described further herein (e.g., in connection with FIGS. 5-7), the data values may be outputted by the output component 333 from a selected one of the arrays when there is a match determined by the comparator circuitry 332 between the data values of the single data file 102 stored by array 308-0 and array 308-1, by array 308-0 and array 308-2, or by array 308-1 and array 308-2.

The output component 333 may be further configured to send the data values from the one array to a serializer 334 formed on chip 336 for output to a functionality 338 formed off chip 337. The serializer 334 may be configured to reconstruct the n portions of the single data file 102, moved via a data bus (e.g., a kn-bit data bus) 307 from one of the three arrays 308-0, 308-1, 308-2 to the serializer 334, into a single sequence of data values (bits). The single sequence of data values of the single data file 102 may be sent via a data bus (e.g., a k-bit data bus) 304 from the serializer 334 to the functionality 338. The functionality 338 shown in FIG. 3 may be one of a plurality of off chip functionalities that enable and/or control various operations (e.g., each functionality may enable and/or control performance of a single operation and/or set of operations that is different from those enabled and/or controlled by another functionality). An identification (e.g., by controller 211) of which particular single data file is being requested (e.g., by a host and/or a functionality), may enable determination of a particular off chip functionality to which the single sequence of data values of the single data file 102 is to be sent.

A notification 335 of no match may, in a number of embodiments, be sent responsive to no match being determined, by the comparator circuitry 332, by comparison of the data values of the single data file 102 stored by array 308-0 and array 308-1, by array 308-0 and array 308-2, or by array 308-1 and 308-2. The notification 335 may be sent to a monitor component 339 coupled to and/or part of the functionality 338. Receipt of such a notification 335 may indicate to the monitor component 339 that none of the sequences of data values (instructions) stored by the three arrays may be relied upon to be without data errors and that the function intended to be performed by the functionality 338 is to be disabled (e.g., due to unintended results potentially occurring from execution of erroneous instructions). Responsive to determination and notification 335 of no match, or a mismatch, between the data values stored by the at least two arrays of the three arrays, the monitor component 339 may enable execution of instructions for a failover functionality (not shown) (e.g., a designated functionality with instructions stored in memory off chip 337). In a number of embodiments, the failover functionality may be executed to perform an alternative function in place of the disabled function (e.g., pulling over and parking an autonomous automobile in an available parking space, among many other possibilities).

In a number of embodiments, a notification 335 also may be sent responsive to determination, by the comparator circuitry 332, of at least one match between the data values redundantly stored by arrays 308-0, 308-1, and/or 308-2. The notification 335 confirming determination of at least one match may be sent to the functionality 338, the monitor component 339, and/or to the host.

Notification 335 of no match being determined by comparison of the data values of the single data file 102 stored by all of the arrays 308-0, 308-1, and 308-2 and/or individually referring to comparison between array 308-0 and array 308-1, between array 308-0 and array 308-2, or between array 308-1 and 308-2 may be provided by a particular signal (e.g., a data value of 0). In contrast, notification 335 of at least one match being determined by comparison of the data values stored by all of the arrays 308-0, 308-1, and 308-2 and/or individually referring to comparison between array 308-0 and array 308-1, between array 308-0 and array 308-2, or between array 308-1 and 308-2 may be provided by a different signal (e.g., a data value of 1) (e.g., as described in connection with FIG. 6 and elsewhere herein).

The notification 335 of no match or at least one match may, in a number of embodiments, be sent off chip 337 directly to the functionality 338, the monitor component 339, and/or to the host via a dedicated data line and/or pin, as indicated in FIG. 3. In a number of embodiments (e.g., where there may not be the dedicated data line and/or pin) the notification 335 may be sent via the serializer 334 and/or a first in/first out (FIFO) queue (not shown). In a number of embodiments, the FIFO queue may be utilized in determination of an order of output from the serializer 334. The notification 335 may, in a number of embodiments, be sent directly, or via the serializer 334 and/or the FIFO queue, off chip 337 to the failover functionality to quickly enable execution of instructions for the alternative function. The notification 335 may be sent as the signal (e.g., either data value 0 or 1) being included at a particular position (e.g., at a last unit interval) of a data burst outputted by the serializer 334 and/or the FIFO queue. Alternatively or in addition, the notification 335 may be sent to the controller 211 on chip 336 for determination of whether to send the notification 335 off chip 337 to the functionality 338, the monitor component 339, the failover functionality, and/or to the host for determination of the alternative function.

In a number of embodiments, responsive to determination by the comparator circuitry 332 of at least one match, the n portions of the single data file 102 may be sent on chip 336 from the comparator circuitry 332 to the serializer 334. The single sequence of data values of the single data file 102 reconstructed by the serializer 334 may be sent from the serializer 334 off chip 337 to the functionality 338 without a notification 335 being sent to the monitor component 339. In contrast, responsive to determination by the comparator circuitry 332 of no match, the notification 335 may be sent off chip 337 to the monitor component 339.

In a number of embodiments, the monitor component 339 may be configured to decide whether and/or what function to enable in response to input of the notification 335 (e.g., when the notification is of no match being determined by the comparator circuitry 332). The monitor component 339 also may be configured for input of a number of signals and/or data from a number of other components and/or systems (e.g., of an autonomous vehicle) to contribute to making the decision whether and/or what function to enable. The monitor component 339 also may be configured to continuously enable the failover functionality and/or performance of the alternative function (e.g., until a determination of a match between at least two arrays for the requested single data file, or until supply of electrical power to the memory device 210 has been resumed following an interruption, among other possibilities).

FIG. 4 is a schematic diagram illustrating an example of a comparator component 440 in accordance with a number of embodiments of the present disclosure. The comparator component 440 illustrated in FIG. 4 may be coupled to, or part of, the comparator circuitry shown at 332 and described in connection with FIG. 3 and/or the comparator circuitry shown at 532 and described in connection with FIG. 5, and elsewhere herein.

In a number of embodiments that have at least three arrays selected from the plurality of arrays for redundant storage of a single data file 102, there may be comparator components 440 of the comparator circuitry 332 corresponding to the number of arrays selected from the plurality of arrays. The number of comparator components may correspond to each different pairing of the at least three arrays. For example, when the number of arrays is three arrays (e.g., arrays 308-0, 308-1, and 308-2) selected from the plurality there may be three comparator components 440 corresponding to the three arrays. The three comparator components 440 may correspond to each of three different pairings of the three arrays (e.g., array X at 308-0 paired with array Y at 308-1, array X at 308-0 paired with array Z at 308-2, and array Y at 308-1 paired with array Z at 308-2). The number of comparator components 440 may each be configured to compare two paired data values (e.g., data values x₀ and y₀, x₁ and y₁, . . . , x_(Q) and y_(Q)) via a logic gate (e.g., logic gates 442-0, 442-1, . . . , 442-Q) corresponding to each paired data value stored by two of the at least three arrays (e.g., array X and array Y).

In a number of embodiments, an n-bit comparator component 440 may compare all kn paired data values (bits) redundantly stored in two arrays (e.g., accessed via kn-bit data buses 107-0 and 107-1 from array X and array Y). For example, all the paired data values x₀ and y₀, x₁ and y₁, . . . , x_(Q) and y_(Q) for the single data file 102 redundantly stored in arrays X and Y may be analyzed using the corresponding logic gates 442-0, 442-1, . . . , 442-Q to determine whether there is a match between each of the paired data values. Each of the logic gates 442 may be, or may include, an XNOR logic gate, as shown in FIG. 4, although embodiments are not limited to the XNOR logic gate. The XNOR logic gate may output a particular signal (e.g., a data value of 1) when particular paired data values accessed from the two arrays match and may output a different signal (e.g., a data value of 0) when different paired data values accessed from the two arrays do not match. The same sort of comparison may be performed for each of the paired data values redundantly stored in array X and array Z and in array Y and array Z.

A differential indicator determined by each of the three comparator components 440 may be utilized to indicate whether comparison of the data values for each of the three different pairings indicates a match for each of the three different pairings of the three arrays. For example, a particular differential indicator signal (e.g., a data value of 1) may be output by logic gate 444 when all of the paired data values from array X and array Y match (X=Y), as determined by output of matching signals (e.g., all data values of 1) from the plurality of logic gates 442. In contrast, a different differential indicator signal (e.g., a data value of 0) may be output by logic gate 444 when all of the paired data values from array X and array Y do not match (X≠Y), as determined by output of non-matching signals (e.g., at least one data value of 0) from the plurality of logic gates 442. The logic gate 444 may be, or may include, an AND logic gate, as shown in FIG. 4, although embodiments are not limited to the AND logic gate. The differential indicators may be used as described in connection with FIG. 6 and/or FIG. 7 and elsewhere herein.

FIG. 5 is a schematic diagram illustrating an example 550 of three arrays selectably coupled to comparator circuitry in accordance with a number of embodiments of the present disclosure. As illustrated in the example 550 shown in FIG. 5, three arrays (e.g., array X at 508-0, array Y at 508-1, and array Z at 508-2), may, in a number of embodiments, be selectably coupled (e.g., via three sets of data lines 507-0, 507-1, and 507-2) on chip 536 to a respective three comparator components (e.g., 540-0, 540-1, and 540-2) of the comparator circuitry 532. The arrays 508 each may be formed in one or more of the alternative embodiments shown at 213, 214, and 216 and described in connection with FIG. 2. The comparator components 540 each may be formed as shown at 440 and operate as described in connection with FIG. 4 or the comparator components 540 each may be formed in a different configuration (e.g., with different logic gates 442 and/or 444 or other differences in the configuration).

Each of the three comparator components 540-0, 540-1, and 540-2 may, in a number of embodiments, be selectably coupled to an output enabler 552 of the comparator circuitry 532. An output component 533 of the comparator circuitry 532 may be configured to output data values of one of the plurality of arrays of the at least three arrays in which the single data file 102 is redundantly stored responsive to determination of a match between the data values stored by a plurality of arrays. The at least three arrays on which the single data file 102 may be redundantly stored may be accessible (e.g., by the controller 211 located on chip 536 and/or a functionality 538, a monitor component 539, and/or host formed off chip 537) via a single network socket and are not accessible via corresponding redundant network sockets for redundant memory.

The output enabler 552 may be configured to enable activation of the output component 533 responsive to determination by the output enabler 552 of a match between the data values stored by, in a number of embodiments, two of three arrays in which the single data file 102 is redundantly stored. For example, when there is a match of the data values of the single data file 102 between at least two of arrays 508-0, 508-1, and/or 508-2, as determined by the respective three comparator components 540-0, 540-1, and 540-2, the output enabler 552 may send an activation signal (e.g., a data value of 1) to the output component 533. The output enabler 552 may be further configured to enable output of a notification 535 (e.g., as shown at 335 and described in connection with FIG. 3) to the monitor component 539 formed off chip 537 responsive to determination by the output enabler 552 of no match between the data values stored by two of the three arrays.

For example, an enablement signal (e.g., a data value of 1) may be output by a logic gate of the output enabler 552 to enable activation of the output component 533 and/or to provide the notification 535. The logic gate of the output enabler 552 may be, or may include, an OR logic gate, as shown in FIG. 5, although embodiments are not limited to the OR logic gate.

The activated output component 533 may be configured (e.g., as a multiplexer) to select between coupling of a first bus 555-0 to a first array (e.g., array X at 508-0) and coupling of a second bus 555-1 to a second array (e.g., array Y at 508-1) responsive to determination of the match between the data values stored by two of the three arrays. The activated output component 533 may access the data values from the first array or the second array based on a valid match (e.g., as described in connection with FIG. 6 and elsewhere herein) with data values stored by a third array (e.g., array Z at 508-2) of the three arrays. The data values accessed from the first array or the second array may be moved via a data bus 507 (e.g., kn-bit data bus shown at 307 and described in connection with FIG. 3) to a serializer 534. The serializer 534 may send the data values accessed from the first array or the second array as a single sequence of data values of the single data file 102 off chip 537 via a data bus 504 (e.g., k-bit data bus shown at 304 and described in connection with FIG. 3). Accordingly, the output component 533 may enable output of the data values corresponding to the valid match from the first array or the second array to the functionality 538 formed off chip 537.

A validation component 554 of the comparator circuitry 532 may be configured to determine a valid match between a first result of comparison between the data values stored by the first array (e.g., array X at 508-0) and the data values stored by the second array (e.g., array Y at 508-1) and a second result of comparison between the data values stored by the first array (e.g., array X at 508-0) and the data values stored by the third array (e.g., array Z at 508-2) of the three arrays. The output enabler 552 activating the output component 533 based on determination of the match between the data values stored by two of three arrays indicates that a valid match exists between either array X or array Y and at least one other array of the three arrays (e.g., either array X matches array Y and/or array Z or array Y matches array X and/or array Z). Hence, either array X at 508-0 or array Y at 508-1 is valid (e.g., or both array X and array Z may be valid). Determination of whether to output the data values from array X or array Z is described in connection with FIG. 7 and elsewhere herein.

The validation component 554 may be further configured to direct that the data values of the valid match (e.g., either from array X or array Y) are output by the activated output component 533 (e.g., via selection and coupling of the first bus 555-0 to array X at 508-0 or via selection and coupling of the second bus 555-1 to array Y at 508-1). For example, a particular validation signal (e.g., a data value of 0) may be output by a logic gate of the validation component 554 to enable output of data values from array X at 507-0 via the activated output component 533. In contrast, a different validation signal (e.g., a data value of 1) may be output by the logic gate of the validation component 554 to enable output of data values from array Y at 507-1 via the activated output component 533. The logic gate of the validation component 554 may be, or may include, an AND logic gate, as shown in FIG. 5. In a number of embodiments, the AND logic gate may have one input coupled to a NOT logic gate, as shown in FIG. 5, although embodiments are not limited to the AND logic gate and/or the NOT logic gate.

FIG. 6 is an example of logic for determination of whether there is a match between data values stored by three arrays in accordance with a number of embodiments of the present disclosure. Logic circuitry (e.g., represented by a truth table shown in FIG. 6) may receive the output of differential indicators (e.g., a data value or 0 or 1, as described in connection with FIG. 4) from comparator components and determinations of validity of the data values stored by the three arrays for determining a valid match (e.g., as described in connection with FIG. 6).

The logic circuitry, represented by the truth table, receives an output from three comparator components (e.g., comparator components shown at 540-0, 540-1, and 540-2 and described in connection with FIG. 5) of the differential indicators to indicate whether there is a match or is not a match for each of three different pairings of the three arrays. The three different pairings of the arrays are shown at column header 660-1 for comparison between array X and array Y, at column header 660-2 for comparison between array Y and array Z, and at column header 660-2 for comparison between array X and array Z. The determinations made from the comparisons of the validity of the data values stored by the three arrays are shown under column header 661.

The logic circuitry is configured to enable determination therefrom (e.g., by controller 211, output enabler 552, validation component 554, and/or another on chip 536 logic-enabled component (not shown)) of whether: the data values stored by all three of the arrays match and are valid 661-8; the data values stored by a particular one of the arrays do not match the data values stored by the other two arrays, which do match and are valid (e.g., as shown for array Y being invalid at 661-2, as shown for array X at 661-3, as shown for array Z at 661-5); and the data values stored by all three of the arrays do not match the data values stored by the other two arrays and are invalid 661-1. Other determinations 661 that may be made from the comparisons are that results of the comparisons are not possible 661-4, 661-6, and 661-7 based upon the data values of one array matching the data values of both of the other arrays, although the data values of both of the other arrays were determined to not match each other (e.g., as indicated at 661-4 showing that the data values of both arrays X and Y match the data values of array Z and also showing that the data values of arrays X and Y not match each other).

FIG. 7 is an example of logic for selection of one array for output of matched data values in accordance with a number of embodiments of the present disclosure. Logic circuitry (e.g., represented by a truth table shown in FIG. 7) may receive (e.g., from validation component 554) a differential signal (e.g., a data value of 1 for a match of the data values in two of the arrays and a data value of 0 for no match of the data values in the two) of whether a valid match has been determined for a first comparison between the data values stored by a first array and the data values stored by a second array (e.g., as shown at column header 760-2 for comparison of array Y as the second array and array Z as the first array) and a second comparison between the data values stored by the first array and the data values stored by a third array of three arrays (e.g., as shown at column header 760-3 for comparison of array X as the third array and array Z as the first array). The logic circuitry, as represented by the truth table, may be configured to enable determination therefrom (e.g., by controller 211, validation component 554, and/or another on chip 536 logic-enabled component) of whether to direct the output component 533 to select the second array (e.g., array Y) or the third array (e.g., array X) for output of the matched data values.

The differential signals resulting from comparisons of the arrays may be utilized for determination of which one array (e.g., as indicated under column header 770) of the matched arrays to select (e.g., based upon a data value of 0 or 1) for output of data values by the output component 533. A data value of 0 may, in a number of embodiments, direct that array X is to be selected and a data value of 1 may direct that array Y is to be selected. For example, as shown at 770-4, the logic circuitry may be configured to enable direction of the second array (e.g., array X) to be selected as a default option for output by the output component 533 responsive to receipt of a signal (e.g., a data value of 0) that a valid match has been determined for both the second array (e.g., array X) and the third array (e.g., array Y) in comparison to the first array (e.g., array Z). The default option of array X may be utilized when a match has been determined (e.g., by output enabler 552), although, as indicated at 770-1, neither array Y nor array X is a match with array Z, meaning that arrays X and Y do match. As shown at 770-2, array Y not matching array Z and array X matching array Z enables selection of array X. As shown at 770-3, array Y matching array Z and array X not matching array Z enables selection of array Z.

As indicated under the column header at 772 labeled “function,” selection of the X array at 772-1, 772-2, and 772-4 may enable (e.g., direct) the output component 533 (e.g., multiplexer) to selectably couple the set of data lines 507-0 and/or the first bus 555-0 for access to the data values of the X array at 508-0. In contrast, selection of the Y array at 772-3 may enable (e.g., direct) the output component 533 to selectably couple the set of data lines 507-1 and/or the second bus 555-1 for access to the data values of the Y array at 508-1.

FIG. 8 is a flow chart of a method 880 for determination of a match between data values stored by three arrays in accordance with a number of embodiments of the present disclosure. Unless explicitly stated, elements of methods described herein are not constrained to a particular order or sequence. Additionally, a number of the method embodiments, or elements thereof, described herein may be performed at the same, or at substantially the same, point in time.

At block 882, the method 880 may, in a number of embodiments, include receiving, by a memory device (e.g., as shown at 210 and described in connection with FIG. 2), a single data file (e.g., as shown at 102 and described in connection with FIG. 1 and elsewhere herein). At block 883, the method 880 may include redundantly storing the single data file on three arrays of memory cells selected from a plurality of arrays formed on chip (e.g., as described in connection with FIGS. 1 and 2 and elsewhere herein). At block 884, the method 880 may include comparing data values of the single data file stored by the three arrays to determine whether there is a match between the data values stored by at least two arrays of the three arrays (e.g., as described in connection with FIGS. 1 and 3-6 and elsewhere herein). At block 885, the method 880 may include outputting data values of one of two arrays of the three arrays responsive to determination of the match between the data values stored by the two arrays (e.g., as described in connection with FIGS. 1, 3-5, and 7 and elsewhere herein).

In a number of embodiments, the method 880 may include interrupting electrical power supplied to the memory device formed on chip. Interrupting the electrical power may result in disabling a function performed by execution of instructions stored by the single data file on chip based at least in part on interrupting the electrical power. Responsive to the function being disabled, the method 880 may include outputting a notification (e.g., as shown at 335 and described in connection with FIG. 3 and elsewhere herein) of the disabled function to enable a failover functionality stored off chip to perform an alternative function (e.g. in place of the disabled function).

Ordinal positioning, as used herein, is used to distinguish between relative positions of elements within respective groups of elements. However, use herein of ordinal numbers such as “first,” “second, and “third” is not intended to indicate a particular ordinal position of an element, unless the context clearly dictates otherwise. For example, consider an array of memory cells having an ordinal position of array 0 and a different array having an ordinal position of array 2 in a plurality of arrays. In this example, array 0 might be referred to as a “first” array and array 1 might be referred to as a “third” array, despite not having an ordinal position of array 3. Alternatively, array 3 might be referred to as a “first” array and array 0 might be referred to as a “second” or “third” array, among other possibilities.

In the above detailed description of the present disclosure, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration how one or more embodiments of the disclosure may be practiced. These embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice the embodiments of this disclosure, and it is to be understood that other embodiments may be utilized and that process, electrical, and structural changes may be made without departing from the scope of the present disclosure.

As used herein, particularly with respect to the drawings, reference numbers with hyphenated digits and/or designators such as “X”, “Y”, “N”, “M”, etc., (e.g., 213-0, 213-1, 213-2, and 213-N in FIG. 2) indicate that a plurality of the particular feature so designated may be included. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used herein, the singular forms “a”, “an”, and “the” include singular and plural referents, unless the context clearly dictates otherwise, as do “a number of”, “at least one”, and “one or more” (e.g., a number of memory arrays may refer to one or more memory arrays), whereas a “plurality of” is intended to refer to more than one of such things. Furthermore, the words “can” and “may” are used throughout this application in a permissive sense (i.e., having the potential to, being able to), not in a mandatory sense (i.e., must). The term “include,” and derivations thereof, means “including, but not limited to”. The terms “coupled” and “coupling” mean to be directly or indirectly connected physically for access to and/or for movement (transmission) of instructions (e.g., control signals, address signals, etc.) and data, as appropriate to the context. The terms “data” and “data values” are used interchangeably herein and may have the same meaning, as appropriate to the context (e.g., one or more data units or “bits”).

While example embodiments including various combinations and configurations of arrays, comparator circuitry, comparator components, output enablers, validation components, output components, functionalities, monitor components, among other circuitry for determination of a match between data values stored by three arrays have been illustrated and described herein, embodiments of the present disclosure are not limited to those combinations explicitly recited herein. Other combinations and configurations of the arrays, comparator circuitry, comparator components, output enablers, validation components, output components, functionalities, monitor components, among other circuitry for determination of a match between data values stored by three arrays disclosed herein are expressly included within the scope of this disclosure.

Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that an arrangement calculated to achieve the same results may be substituted for the specific embodiments shown. This disclosure is intended to cover adaptations or variations of one or more embodiments of the present disclosure. It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. The scope of the one or more embodiments of the present disclosure includes other applications in which the above structures and processes are used. Therefore, the scope of one or more embodiments of the present disclosure should be determined with reference to the appended claims, along with the full range of equivalents to which such claims are entitled.

In the foregoing Detailed Description, some features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the disclosed embodiments of the present disclosure have to use more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. 

What is claimed is:
 1. An apparatus, comprising: a plurality of arrays of memory cells formed on a single memory chip, each array of the plurality of arrays of memory cells configured to receive n portions of k data values (bits) that are deserialized from a single data file comprising k data values via a respective bus of a plurality of kn-bit data buses such that the n portions of the k bits of data are redundantly stored over the plurality of arrays of memory cells; and comparator circuitry comprising an output component coupled directly to a first array and a second array of at least three arrays selected from the plurality such that the output component receives two inputs from the first array and the second array; wherein the comparator circuitry is configured to: compare data values stored by the at least three arrays selected from the plurality to determine whether the first array or the second array stores a data value matched by more than half of the at least three arrays; enable the output component to access, in response to the matched data value being determined to be stored in the first array, the first array to output the matched data value; and provide, in response to a determination that there is no match between the data values stored by the at least three arrays, a notification indicating no match between the data values stored by the at least three arrays.
 2. The apparatus of claim 1, wherein the comparator circuitry is configured to compare data values of a single data set stored by the three arrays.
 3. The apparatus of claim 1, wherein the three arrays are each formed in a same configuration of memory cells on the single memory chip.
 4. The apparatus of claim 1, wherein: the plurality of arrays of memory cells formed on the single memory chip is formed on an autonomous vehicle; and the apparatus comprises other memory off the single memory chip, the other memory storing instructions executable for a failover functionality for execution responsive to determination of no match or a mismatch between the data values stored by the at least two arrays of the three arrays.
 5. The apparatus of claim 1, wherein the comparator circuitry is further configured to determine whether the first array or the second array stores the data value matched by more than half of the three arrays based upon an adjustable threshold number of mismatches of data values stored by two of the arrays.
 6. The apparatus of claim 5, wherein the adjustable threshold number is adjusted to no mismatches.
 7. The apparatus of claim 1, further comprising: three comparator components of the comparator circuitry corresponding to the three arrays selected from the plurality; an output enabler of the comparator circuitry configured to enable activation of the output component responsive to determination by the output enabler of a match between the data values stored by more than half of the three arrays; a validation component of the comparator circuitry configured to determine a valid match between a first result of comparison between the data values stored by a first array and the data values stored by a second array and a second result of comparison between the data values stored by the first array and the data values stored by a third array of the three arrays; and the validation component further configured to direct that the data values of the valid match are output by the activated output component.
 8. The apparatus of claim 1, further comprising an output enabler of the comparator circuitry configured to enable output of a notification to a monitor component formed off the single memory chip responsive to determination by the output enabler of no match between the data values stored by two of the three arrays.
 9. The apparatus of claim 1, further comprising: three comparator components of the comparator circuitry corresponding to three arrays selected from the plurality, wherein the three comparator components correspond to each of three different pairings of the three arrays; and a differential indicator determined by each of the three comparator components to indicate whether comparison of the data values for each of the three different pairings indicates a match for each of the three different pairings of the three arrays.
 10. The apparatus of claim 1, further comprising: logic circuitry configured to: receive an output from three comparator components of differential indicators to indicate whether there is a match or is not a match for each of three different pairings of the three arrays; and enable determination therefrom of whether: the data values stored by all of the at least three of the arrays match; the data values stored by a particular one of the arrays do not match the data values stored by the other two arrays, which stores a data value matched by more than half of the at least three arrays; and the data values stored by all three of the arrays do not match the data values stored by the other remaining arrays.
 11. The apparatus of claim 1, further comprising: the output component further configured to: select between coupling of a first bus to a first array and coupling of a second bus to a second array responsive to determination of a match between the data values stored by more than half of the at least three arrays; access the data values from the first array or the second array based on a valid match with data values stored by a third array of the at least three arrays; and output the data values corresponding to the valid match from the array to a functionality formed off the single memory chip.
 12. The apparatus of claim 1, further comprising: logic circuitry configured to: receive from a validation component a differential signal of whether a valid match has been determined for a first comparison between the data values stored by a first array and the data values stored by a second array and a second comparison between the data values stored by the first array and the data values stored by a third array of the at least three arrays; and enable determination therefrom of whether to direct the output component to select the second array or the third array for output of the stored data values.
 13. The apparatus of claim 12, wherein the truth table is configured to enable direction of the output component to select the second array as a default option responsive to receipt of a signal that a valid match has been determined for both the second array and the third array in comparison to the first array.
 14. A system, comprising: a plurality of arrays of memory cells formed on a single memory chip, each array of the plurality of arrays of memory cells configured to receive n portions of k data values (bits) that are deserialized from a single data file comprising k data values via a respective bus of a plurality of kn-bit data bus such that the n portions of the k bits of data are redundantly stored over the plurality of arrays of memory cells; and comparator circuitry comprising an output component coupled directly to a first array and a second array of the at least three arrays selected from the plurality of the arrays of memory cells such that output component receives two inputs from the first array and the second array; wherein the comparator circuitry is configured to: compare data values of the single data file stored by the at least three arrays to determine whether there is a match between the data values stored by more than half of the at least three arrays; determine, responsive to determination of the match, which one of the first array and the second array stores the matched data value; enable, responsive to determination of one of the first array and the second array storing the matched data value, the output component to access one of the first array and the second array; and provide, in response to a determination that there is no match between the data values stored by the at least three arrays, a notification indicating no match between the data values stored by the at least three arrays.
 15. The system of claim 14, wherein the comparator circuitry comprises a number of comparator components corresponding to each different pairing of the at least three arrays.
 16. The system of claim 14, wherein the comparator circuitry comprises a number of comparator components each configured to compare two paired data values via a logic gate corresponding to each paired data value stored by more than half of the at least three arrays.
 17. The system of claim 14, wherein the at least three arrays on which the single data file is redundantly stored are accessible via a single network socket.
 18. The system of claim 14, wherein the at least three arrays on which the single data file is redundantly stored are not accessible via corresponding redundant network sockets for redundant memory.
 19. The system of claim 14, further comprising: a controller configured to: receive a request for the single data file; and direct the comparator circuitry to access the data values stored by the at least three arrays to determine whether there is the match.
 20. The system of claim 14, wherein the at least three arrays selected from the plurality for redundant storage of the single data file are each formed on the single memory chip in a dynamic random access memory (DRAM) configuration.
 21. The system of claim 14, wherein the at least three arrays each correspond to a different bank group, each different bank group having a plurality of memory banks formed on the single memory chip.
 22. The system of claim 14, wherein the at least three arrays each correspond to a different memory bank formed on the single memory chip.
 23. The system of claim 14, wherein the at least three arrays each correspond to a different section of a single memory bank formed on the single memory chip.
 24. A method for operating a memory device, comprising: receiving, by the memory device, a single data file as k data values (bits) at a time on a k-bit data bus; deserializing the k bits of data into a number (n) of portions using a deserializer coupled to the k-bit data bus; redundantly storing the n portions of the k bits of data as the single data file on three arrays of memory cells selected from a plurality of arrays formed on a single memory chip; comparing, by using a number of comparators components, data values of the single data file stored by the three arrays to determine whether there is a match between the data values stored by more than half of the three arrays; in response to determining that there is a match between the data values stored by more than half of the three arrays: transferring, by accessing one of the three arrays that is coupled to an output component and storing the matched data value, the matched data value directly from the one of the three arrays to the output component without transferring the matched data value through the number of comparator components; and in response to determining that there is no match between the data values stored by the three arrays: providing a notification indicating no match between the data values stored by the at least three arrays.
 25. The method of claim 24, further comprising sending the matched data value from the one of the three arrays to a serializer formed on the single memory chip for output to a functionality formed off the single memory chip.
 26. The method of claim 24, further comprising storing the single data file in parallel on the three arrays via three sets of data lines separately coupled to the three arrays.
 27. The method of claim 24, further comprising: storing the single data file on a first array of the three arrays via a set of data lines coupled to the first array; and performing a copy function on the single data file stored on the first array to redundantly store the single data file on a second array and on a third array of the three arrays.
 28. The method of claim 24, further comprising: interrupting electrical power supplied to the memory device formed on the single memory chip; disabling a function performed by execution of instructions stored by the single data file on the single memory chip based at least in part on interrupting the electrical power; and outputting a notification of the disabled function to enable a failover functionality stored off the single memory chip to perform an alternative function. 